Shinji Kagawa has calmed fears over a reported back injury that led him to pull out of Japan's World Cup qualifier against Iraq.

Kagawa, 23, was withdrawn from the game an hour before kick-off as a result of a problem he had sustained in training. Japan coach Alberto Zaccheroni had felt he was fit enough to take a place on the bench but opted not to risk the Manchester United player.

However the midfielder is not too worried about the problem and does not believe he will be sidelined for long.

"I felt a twinge in the back during practice when I was on the ball. I had some treatment but didn't want to risk causing the team trouble by playing," Kagawa told the Kyodo news agency.

"Obviously it's a shame I wasn't able to play... It's not that serious and I don't think it will keep me out for long."

Japan won the game 1-0 courtesy of a Ryoichi Maeda goal in the 25th minute.

Kagawa joined United in the summer after helping Dortmund win back-to-back Bundesliga titles and made an immediate impression at Old Trafford, scoring on his home debut against Fulham. United host Wigan on Saturday and it remains to be seen if Kagawa will be able to feature.

Meanwhile, Darren Fletcher will continue his comeback from a serious bowel problem when he plays for a United reserve team against Stalybridge Celtic on Tuesday night. Summer signing Alexander Buttner, who was brought to the club to be Patrice Evra's deputy at left-back, is also set to start.